1. Field of the Invention
The invention relates to a method for the continuous production of a multidirectional fabric web.
2. Discussion of Background Information
Bidirectional and multidirectional fabric constructions as well as methods for their production are known. Such fabrics are used, among other things, as textile reinforcing structures in bonded fiber applications, primarily with a layer structure of ±45°. However, for many applications, the bidirectional or multidirectional reinforcement in the ±α direction is not sufficient. Here at least one further layer with 0° orientation is needed. This additional material layer is required in order to be able also to absorb forces in the 0° direction in addition to the loads in the ±α direction in the later bonded fiber component.
In EP 768167 a method is described with which a fabric is produced that is biaxially reinforced preferably in the ±45° direction. A unidirectional fiberwoven fabric that has been preset by an adhesive thread grid and that is winding onto a revolving work plate at the folding angle ±α to the production direction of the biaxial fabric, is thereby converted into a two-layer fabric web in a fold-winding process. The two-layer fabric web is drawn off from the revolving work plate by a transport device and is bonded by a pair of pressure rolls.
During the drawing-off and spreading-out of the biaxial fiber layers from the revolving work plate which are pre-set only by the mesh-like structure of the applied adhesive threads, distortion of the laid-down fiber layers occurs. Without the presence of a stabilizing support layer in the form of a transport aid in the production direction, which absorbs in the biaxial fabric construction the stresses in the fabric occurring during the drawing-off, spreading-out and transporting of the fabric, a distortion-free setting with the strived—for high surface quality over the entire fabric width of the fiber layers laid down in the ±α orientation, is possible only with great difficulty.
In EP 768167 moreover the possibility is mentioned of calender-coating the needed 0° layer and/or additional material layers onto the finished ±α fabric in a further additional step separate from the fabric-forming process. However, this does not eliminate the above-mentioned problems. Also, it is no longer possible in this manner to fulfill the requirement for a 0° layer arranged between the two angle layers.
JP 2003-221771 describes a device for the production of biaxial fabrics. Likewise in a fold-winding process, one or more material webs fed laterally at an angle of ±α to the production direction of the biaxial fabric are wound onto interior stationary edge elements that are arranged in pairs at a distance from one another. On the edge elements, double-sided adhesive tapes to fix the two layers on top of one another are brought into the interior of the fabric tube. The fabric tube is drawn off from the interior edge elements, spread out, and bonded by a pair of pressure rolls.
A disadvantage of this is the insertion of the double-sided adhesive tapes into the edge areas of the fabric, which lead to a varying thickness in the fabric. As a result, the thickened edges must either be removed in an additional operation or be accepted as a quality defect. Moreover the edge areas of the fabric are formed by the edge elements at a considerable distance, since between the edge elements, the covering tapes to be drawn off from the double-sided adhesive tapes must be guided back out of the folding zone. Distortions in the fabric are generated thereby during the drawing-off of the fabric tube. Also, the introduction of a stabilizing inner 0° layer is not possible with this device, so that the resulting fabric web has no distortion stability in the production direction.